In wheat, the post-flowering period largely controls both yield and grain protein content. Our objective was to characterize genotypic differences for nitrogen (N) absorption and remobilisation under limiting and non limiting fertilization conditions. Five winter wheat cultivars were grown in the field for two years at two N levels. 15N was applied at flowering to evaluate N absorption and remobilisation. Marker enzyme activities for N assimilation and recycling and N metabolite contents were monitored on the flag leaf and the upper internode. We showed that the use of 15N- labelling was a reliable method to assess post-flowering N absorption and remobilisation. This approach revealed that on average 71.2 percent of grain N came from remobilisation with significant genotypic differences for the amount of N absorbed and remobilised. Significant differences were found for N remobilisation efficiency estimated as plant N at anthesis on N remobilised to the grain and for N translocation efficiency which corresponds to N absorbed after flowering that is translocated to the grain. Significant genotypic differences were also found for all enzymes activities and metabolites used as representative markers for N assimilation and recycling. Glutamine synthetase activity was highly correlated to remobilised N and to grain yield, while nitrate reductase activity was correlated to absorbed N and to grain N content.